1. Field of the Invention
This invention relates to a filter for the purification of platelets. More particularly, it relates to a filter through which is passed a platelet suspension thereby effecting selective removal of leucocytes as extraneous matter therefrom and consequent separation of platelets in a purified form.
2. Description of the Prior Art
Today, the form of blood transfusion is increasingly tending from the whole blood transfusion toward the component blood transfusion using only the blood component required for a given patient. The number of kinds of medicines using platelets is increasing year after year. In recent years, the transfusion of platelets has been steadily gaining in importance in proportion to continuous increase of patients of thrombocytopania caused by heavy dosage of chemotherapeutic agents used against malignant tumors.
The platelet medicines actually put to use to date include the bag PC (platelet concentrate) prepared after collection of blood in a bag and the apheresis PC obtained by the use of a component blood collecting device. They both require separation of platelets from blood by the method of centrifugal separation.
The current method of centrifugal separation, however, inevitably suffers leakage of leucocytes (mainly lymphocytes) into the PC. It has been found that the leucocytes in the PC induce fever and other similar secondary effects after the transfusion of platelets and most patients taking frequent transfusion of platelets acquire refractoriness to the effect of transfusion. These adverse effects are logically explained by a supposition that the leucocytes give rise to human leucocyte antigen (HLA) and lymphocytetoxic antigen (LCT) in the patients' body.
The platelet transfusion is required to be performed frequently in large doses. The patient is consequently affected by many and unspecified antigens. It is said that the LCT antigen is detected in not less than 90% of the patients taking transfusion of 100 units or more of platelet medicine. When platelets are transfused into patients who have already developed such antibodies, the transfusion manifests the expected effect because the platelets are prone to destruction in the patients' bodies.
Various types of filters have been developed for the removal of leucocytes and have been already introduced to the market. They are either formed by having various kinds of fibers such as natural fibers like natural cellulose, synthetic fibers of polyesters, polyamides, and polyacrylonitrile, and inorganic fibers like glass fibers simply packed in their unmodified form in columns or provided with a filter part of secondarily fabricated non-woven fabric. They are chiefly intended to remove leucocytes mingling into such an erythrocyte medicine as the CRC (concentrated red corpuscles). Though these filters for the removal of leucocytes manifest their performance above a certain level concerning the removal of leucocytes, they are not prevented from removing platelets at the same time. They bring about an improper effect, therefore, when they are used for the removal of leucocytes from a platelet suspension or from whole blood.
In the circumstances, a desire has been expressed for a method or apparatus for permitting transfusion of pure platelets by removal of leucocytes, particularly lymphocytes, from such blood components as platelet suspensions and whole blood which contains leucocytes and platelets.
An object of the present invention, therefore, is to provide a novel filter for the purification of platelets.
Another object of this invention is to provide a filter for the purification of platelets, which filter is capable of selectively removing leucocytes a extraneous matter from such blood components as platelet suspensions and whole blood which contain leucocytes and platelets.